Optimization for aliases Optimized AliasAdd() and AliasGet() by avoiding the usage of Tcl_SetVar2Ex() and Tcl_GetVar2Ex(). This change improves the performance of AliasAdd() by ~20% and AliasGet() by 10%. Strangely, Tcl does not provide an interface to the Tcl_Obj-based TclObjUnsetVar2(), which is used internally by Tcl_UnsetVar2()), such we could also avoid the latter.